Harmonic oscillations of the voltage are an important parameter when evaluating the power quality of electric grids. With the rising number of electronic components that are either fed by or feeding into the grid with inverters, harmonic oscillations have increasingly become a topic of research, since these inverter driven components are a source of them. Especially in grids with a high penetration of these components, like photovoltaic and wind power plants, battery storage systems, electric vehicles or modulating heat pumps, the limits of harmonic oscillations as specified in the EN 50160 are often exceeded without some kind of compensation.

For this reason, this paper looks into the ability of grid forming inverters to compensate harmonic oscillations of the voltage. The ability to act as a sink for harmonic voltage oscillations is a demanded characteristic for inverter controls to be classified as grid forming. In this paper three methods are used to analyse this ability. At first, an analytical approach is chosen to identify the frequency range in which the grid forming inverter control is damping harmonic voltage oscillations of the external grid. This analytical approach is then verified in simulations, whose scope is then extended to replicate a real voltage grid from a field measurement campaign of the research project “Fuchstal-leuchtet”. This extended simulation grid is then used to compare results of a field measurement campaign to the simulated and analytical results. The grid of the field measurement campaign consists of two grid forming inverters with a power rating of 3 MVA each, which supply an island grid. Furthermore, there are four wind power plants with a combined rated power of 12 MVA and a power-to-heat unit with a power rating of 4.7 MVA in the grid. For the purpose of analysing harmonic voltage oscillations and the ability of grid forming inverters to dampen them, multiple power setpoints of the wind power plants and the power-to-heat unit looked into with either one or both grid forming inverters active in order to compare the impact of the share of grid forming inverters on the total power in a grid.

The goal of this paper is to analyse and quantify the ability of grid forming inverters to act a sink for harmonic voltage oscillations, to identify the impact of parameterisation of the inverter control on this ability and lastly to assess the accuracy of analytical and simulation based approaches to replicate this behaviour.